**4. Case studies of skin lesions in cetaceans – The signs?**

128 New Approaches to the Study of Marine Mammals

*Trichophyton,* as well as *Verticillium* [16, 23-25].

ecosystems. Plants, humans and animals are subsequently exposed to a variety of potentially infectious microbes. Fungal genera known to harbour keratinophilic species include: *Acremonium, Alternaria. Aspergillus, Candida, Chaetomium, Chrysosporium, Cladosporium, Curvularia, Fusarium, Geotrichum, Gliocladium, Gymnoascus, Microsporum, Monoascus, Mucor, Paecilomyces, Penicillium, Scopulariopsis, Sporothrix, Trichoderma,* 

**Figure 2.** Light micrographs of keratinophilic fungi. a. Fruit body of *Chaetomium murorum* with long ascomatal setae; b. ascomatal setae and ascospores of *Chaetomium murorum*; c. conidia of *Alternaria* 

Some keratinophilic fungi (Figure 2) are known to be pathogenic, and often the cause of cutaneous skin infections. These include the so-called dermatophytes, belonging to the genera *Epidermophyton, Microsporum* and *Trichophyton,* as well as non-dermatophytes such as *Aspergillus, Candida, Fusarium* and *Scopulariopsis* spp*.* Moreover, De Hoog et al. [16] remarked that more cases of fungal infections seem to be caused by fungal spp. formerly known as being saprobic, and appear to be associated with the increasing numbers of immuno-compromised patients. These fungi are mostly opportunists that cause infection when the immune system of the host is breached [16, 17]. Interestingly, of more than 100 000 known fungal species, only about 100 have been reported regularly, as infectious agents of

Certain species of the bacterial genus *Bacillus* also have the ability to produce keratinases. *Bacillus cereus, Bacillus licheniformis* and *Bacillus subtilis* have been identified and studied in

*alternata*; d. Fertile hyphae of *Chrysosporium keratinophilum* bearing conidia

animals, as well as humans [16].

Skin lesions in cetaceans have been reported since the 1950's [2]. Some examples of the steady stream of reports in later years are presented below.

Skin lesions containing *Staphylococcus* were reported for the first time in cetaceans in 1988 [27]. In that study, two isolates of *Staphylococcus* were obtained from purulent tissue that occurred in two captive dolphins with multiple, suppurating lesions, and subsequently described as a new species, *Staphylococcus delphini*.

A study conducted over a four year period found that a range of microbes were associated with lesional and non-lesional skin in a group of bowhead whales (*Balaena mysticetus*), characterized by dozens to hundreds of roughened areas on their skin surfaces [28]. The majority of microbes, isolated during the study, were associated with the lesional skin: 56% of Gram positive bacteria, 75% of Gram negative bacteria and 64% of the yeasts. Also, the lesional skin was characterized by the presence of *Corynebacterium* spp.*, Acinetobacter* spp., as well as representatives of *Moraxella*. *Candida* spp. were the dominant yeast species, followed by representatives of *Cryptococcus* and *Rhodotorula.* Subsequent tests on the isolates showed the production of enzymes able to cause necrosis by microbes originating from both lesional and non-lesional skin. These whales occurred in regions with increased industrial activities (gas and oil exploration) in the Beaufort Sea; the authors speculated that the roughened skin areas might have been associated with the adherence of spilled oil [28].

A study examining skin diseases among wild cetaceans from British waters found 69% of individuals to be affected [29]. The authors reported wounds and other traumatic injuries, as well as lesions caused by pox and herpes viruses, as well as bacteria, ectoparasites and nonspecific ulcers. Concerns that the lesions were associated with pollution were raised but not confirmed [29].

Henk and Mullan [30] examined 23 bowhead whales and reported shallow lacerations, circular depressions and epidermal sloughing on these whales' skin. The authors also found abundant bacteria and diatoms associated with these lesions, and even higher numbers where the stratum spinosum was exposed. The bacterial isolates were found to include cocci, bacilli and filamentous spp., with increasing numbers associated with higher levels of necrotic decay. Protozoa and fungi were also observed and also increased in incidence with more disturbed epidermal surfaces. The authors also identified several erosive enzymes from these microbes and suggested an association between the whales' skin and spilled oil.

A pygmy sperm whale (*Kogia breviceps*) and an Atlantic white-sided dolphin (*Lagenorhynchus acutus*) were reported with mycotic dermatitis, in the form of raised, firm, erythemous, cutaneous nodules on parts of their bodies [31]. The dermatitis cases were the result of

infections caused by a species of *Fusarium*, and in both cases, the disease was preluded by stress factors, such as stranding, which presumably induced immuno-suppression.

Cutaneous Lesions in Cetaceans: An Indicator of Ecosystem Status? 131

Between the years 2006 and 2009, Van Bressem and co-workers published extensively on many cases of skin lesions in a range of cetaceans. In one such study [38], the authors examined 'tattoo' skin lesions caused by poxvirus infections in four species of small cetaceans (*Lagenorhynchus obscurus, Delphinus capensis, T. truncatus* and *Phocoena spinipinnis*) near Peru. They reported a possible increase in the disease since 1990 in two of the species (*L. obscurus* and *P. spinipinnis*). They also found that male *P. spinipinnis* individuals were two

A population of long-beaked common dolphins (*D. capensis*) was studied between 1985 and 2000 in the Southeast Pacific near Peru, characterised by extensive fisheries activities [39]. The authors reported the presence of a variety of cutaneous lesions, abnormalities and scars, on between 1.8% and 48.2% of these dolphins. Tattoo lesions, punctiform and round marks, dark circle lesions, coronet marks and abnormal pigmentation were described, among many other abnormalities in this population. These lesions were attributed to pox- and herpes

An extensive survey conducted from 1984 until 2007 and dealing with previously unreported cases of skin and skeletal diseases in cetaceans from Ecuador, Colombia, Peru, Chile, Argentina, Uruguay, Brazil and Venezuela, was presented as an overview in 2007 [40]. The authors reported tattoo skin disease, lobomycosis-like disease and other cutaneous infections with unknown aetiology in 590 cases, out of a total of 7635 specimens, including 12 different odontocete spp. that were examined. It was suggested that anthropogenic factors, including aquaculture, fish factories, untreated waste water, ballast water and chemical pollution, play a major role in the degradation of the habitats of these cetaceans, thereby contributing to the poor health status of many individuals in these populations.

Chronic mycotic disease of the skin and subdermal tissues in Indo-Pacific bottlenose dolphins (*Tursiops aduncus*), caused by the fungus *Lacasia loboi,* was reported in 2009 [41]. These dolphins lived in the tropical lagoon of Mayotte, situated in the Indian Ocean between Mozambique and Madagascar, and were characterized by numerous raised, greyish nodules on the head, flanks, dorsal fin, belly, back and tail. In some individuals, the lesions appeared to be quite severe and lesions resembling other unknown fungal infections were also observed. Habitat degradation, especially along the coastal areas where rapid urbanization, agricultural activities and untreated waste water are evident, was mentioned

Inshore and offshore surveys conducted, from 1997 to 2007, on bottlenose dolphins in the larger Santa Monica Bay, California, revealed a very high incidence and extent of skin lesions [42]. Causative agents found included bacteria, viruses, fungi, vitamin deficiencies, diatom growth and parasites. However, anthropogenic activities were thought to be a major contributing factor and seemed to be linked to especially viral outbreaks. Moreover, this area (the Southern California Bight) is known for high concentrations and volumes of pollutants entering the coastal and offshore environment, as well as contaminated sediments that cover a 44 km² on the ocean floor, containing dichloro-diphenyl-trichloro-

times more infected than their females [38].

viruses, as well as other unknown viruses and parasites.

as a contributing factor to the aetiology of the disease.

ethane (DDT) and polychlorinated biphenyls (PCBs).

Resident bottlenose dolphins, from the Sado estuary in Portugal, were examined and 85% of the community showed signs of skin disorders [32]. The authors compared these results to observations from other areas, and came to the conclusion that habitat degradation played a significant role in these disorders since eutrophication seemed to a serious problem in this estuary. Consequently, the authors attributed these conditions to apparent depressed immune systems caused by stress, habitat degradation and pollution.

Ten coastal populations of bottlenose dolphins served in a photographic study that compared levels of epidermal disease among populations exposed to a wide range of natural and anthropogenic conditions [33]. It was found that epidermal lesions were common in all populations. However, the severity and prevalence of the different classes of lesions, varied among the populations. Those occurring in areas with lower water salinity and temperature had a higher lesion incidence and severity. On the other hand, no direct correlation was found between the lesion characteristics and toxicology data. The authors concluded that the oceanographic variables might influence the epidermal integrity of the skin or cause physiological stress, thereby rendering these mammals more prone to natural infections or impact by anthropogenic activities.

In 2001, Mikaelian and co-workers [34] reported a case of six beluga whales (*Delphinapterus leucas*) with slightly depressed, greyish round lesions, found dead on the shores of the St. Lawrence estuary. Histology of the lesions revealed *Dermatophilus*-like actinomycetes that had invaded the stratum corneum of the epidermis [34]. Even the stratum spinosum of these animals were characterized by marked spongiosis and vacuolar degeneration. These whales were furthermore free from ectoparasites, thereby eliminating the possibility of this predisposing factor. Immunodeficiency seemed to be the most likely cause of these *Dermatophilus*-like infections, since four of the six individuals were characterized by chronic debilitating diseases. Martineau [35] followed this up by reporting on an extensive survey (1983-1999) on the beluga whales from this estuary. They found cancer rates in these animals to be much higher than in any other population of cetaceans, similar to that of other mammals (including humans) from the same area. They believed that environmental contaminants, such as polycyclic hydrocarbons (PAH) were involved in the aetiology of these conditions.

A visual health assessment study in North Atlantic right whales (*Eubalaena glacialis*) revealed a variety of skin conditions, as well as the calving intervals in these mammals increasing from 3.67 to 5 years, thereby significantly impacting on the population growth [36]. The authors speculated that possible causes might include environmental contaminants, marine bio-toxins, nutritional stress, genetic influences, as well as infectious diseases.

Hamilton and Marx [37] presented results of a study conducted from 1980 until 2002 on skin lesions among North Atlantic right whales. The authors documented white, blister, swath and circular lesions. White lesions appeared to represent episodic events, the incidence of blister lesions were more constant, whereas swath lesions were often associated with fatal conditions. They reckoned that skin lesions are indicators of compromised health, possibly caused by deteriorating habitat quality in coastal areas.

Between the years 2006 and 2009, Van Bressem and co-workers published extensively on many cases of skin lesions in a range of cetaceans. In one such study [38], the authors examined 'tattoo' skin lesions caused by poxvirus infections in four species of small cetaceans (*Lagenorhynchus obscurus, Delphinus capensis, T. truncatus* and *Phocoena spinipinnis*) near Peru. They reported a possible increase in the disease since 1990 in two of the species (*L. obscurus* and *P. spinipinnis*). They also found that male *P. spinipinnis* individuals were two times more infected than their females [38].

130 New Approaches to the Study of Marine Mammals

infections caused by a species of *Fusarium*, and in both cases, the disease was preluded by

Resident bottlenose dolphins, from the Sado estuary in Portugal, were examined and 85% of the community showed signs of skin disorders [32]. The authors compared these results to observations from other areas, and came to the conclusion that habitat degradation played a significant role in these disorders since eutrophication seemed to a serious problem in this estuary. Consequently, the authors attributed these conditions to apparent depressed

Ten coastal populations of bottlenose dolphins served in a photographic study that compared levels of epidermal disease among populations exposed to a wide range of natural and anthropogenic conditions [33]. It was found that epidermal lesions were common in all populations. However, the severity and prevalence of the different classes of lesions, varied among the populations. Those occurring in areas with lower water salinity and temperature had a higher lesion incidence and severity. On the other hand, no direct correlation was found between the lesion characteristics and toxicology data. The authors concluded that the oceanographic variables might influence the epidermal integrity of the skin or cause physiological stress, thereby rendering these mammals more prone to natural

In 2001, Mikaelian and co-workers [34] reported a case of six beluga whales (*Delphinapterus leucas*) with slightly depressed, greyish round lesions, found dead on the shores of the St. Lawrence estuary. Histology of the lesions revealed *Dermatophilus*-like actinomycetes that had invaded the stratum corneum of the epidermis [34]. Even the stratum spinosum of these animals were characterized by marked spongiosis and vacuolar degeneration. These whales were furthermore free from ectoparasites, thereby eliminating the possibility of this predisposing factor. Immunodeficiency seemed to be the most likely cause of these *Dermatophilus*-like infections, since four of the six individuals were characterized by chronic debilitating diseases. Martineau [35] followed this up by reporting on an extensive survey (1983-1999) on the beluga whales from this estuary. They found cancer rates in these animals to be much higher than in any other population of cetaceans, similar to that of other mammals (including humans) from the same area. They believed that environmental contaminants, such

as polycyclic hydrocarbons (PAH) were involved in the aetiology of these conditions.

nutritional stress, genetic influences, as well as infectious diseases.

caused by deteriorating habitat quality in coastal areas.

A visual health assessment study in North Atlantic right whales (*Eubalaena glacialis*) revealed a variety of skin conditions, as well as the calving intervals in these mammals increasing from 3.67 to 5 years, thereby significantly impacting on the population growth [36]. The authors speculated that possible causes might include environmental contaminants, marine bio-toxins,

Hamilton and Marx [37] presented results of a study conducted from 1980 until 2002 on skin lesions among North Atlantic right whales. The authors documented white, blister, swath and circular lesions. White lesions appeared to represent episodic events, the incidence of blister lesions were more constant, whereas swath lesions were often associated with fatal conditions. They reckoned that skin lesions are indicators of compromised health, possibly

stress factors, such as stranding, which presumably induced immuno-suppression.

immune systems caused by stress, habitat degradation and pollution.

infections or impact by anthropogenic activities.

A population of long-beaked common dolphins (*D. capensis*) was studied between 1985 and 2000 in the Southeast Pacific near Peru, characterised by extensive fisheries activities [39]. The authors reported the presence of a variety of cutaneous lesions, abnormalities and scars, on between 1.8% and 48.2% of these dolphins. Tattoo lesions, punctiform and round marks, dark circle lesions, coronet marks and abnormal pigmentation were described, among many other abnormalities in this population. These lesions were attributed to pox- and herpes viruses, as well as other unknown viruses and parasites.

An extensive survey conducted from 1984 until 2007 and dealing with previously unreported cases of skin and skeletal diseases in cetaceans from Ecuador, Colombia, Peru, Chile, Argentina, Uruguay, Brazil and Venezuela, was presented as an overview in 2007 [40]. The authors reported tattoo skin disease, lobomycosis-like disease and other cutaneous infections with unknown aetiology in 590 cases, out of a total of 7635 specimens, including 12 different odontocete spp. that were examined. It was suggested that anthropogenic factors, including aquaculture, fish factories, untreated waste water, ballast water and chemical pollution, play a major role in the degradation of the habitats of these cetaceans, thereby contributing to the poor health status of many individuals in these populations.

Chronic mycotic disease of the skin and subdermal tissues in Indo-Pacific bottlenose dolphins (*Tursiops aduncus*), caused by the fungus *Lacasia loboi,* was reported in 2009 [41]. These dolphins lived in the tropical lagoon of Mayotte, situated in the Indian Ocean between Mozambique and Madagascar, and were characterized by numerous raised, greyish nodules on the head, flanks, dorsal fin, belly, back and tail. In some individuals, the lesions appeared to be quite severe and lesions resembling other unknown fungal infections were also observed. Habitat degradation, especially along the coastal areas where rapid urbanization, agricultural activities and untreated waste water are evident, was mentioned as a contributing factor to the aetiology of the disease.

Inshore and offshore surveys conducted, from 1997 to 2007, on bottlenose dolphins in the larger Santa Monica Bay, California, revealed a very high incidence and extent of skin lesions [42]. Causative agents found included bacteria, viruses, fungi, vitamin deficiencies, diatom growth and parasites. However, anthropogenic activities were thought to be a major contributing factor and seemed to be linked to especially viral outbreaks. Moreover, this area (the Southern California Bight) is known for high concentrations and volumes of pollutants entering the coastal and offshore environment, as well as contaminated sediments that cover a 44 km² on the ocean floor, containing dichloro-diphenyl-trichloroethane (DDT) and polychlorinated biphenyls (PCBs).

A study conducted during 2006 and 2007 revealed notable differences in skin diseases between two communities of Guiana dolphins (*Sotalia guianensis*) from Brazil [43].The authors found that the community, living in the chemically and biologically polluted Paranaguá estuary, was characterized by the occurrence of lobomycosis-like and nodular skin diseases. This estuary is known for its high levels of chlorinated hydrocarbons, as well as regular oil spills. In contrast, another community of Guiana dolphins, living in the less polluted Cananéia estuary, was free from these skin diseases and had relatively low tissue levels of organochlorines. The authors consequently proposed that lobomycosis-like and nodular skin diseases might act as indicators of environmental burden.

Cutaneous Lesions in Cetaceans: An Indicator of Ecosystem Status? 133

It seems evident from the above mentioned studies that the occurrence and high prevalence of skin lesions in many cetacean populations are linked to environmental factors, including water salinity and temperature, as well as pollution and eutrophication. These skin lesions may be caused by a wide diversity of microbes that will be discussed in the

*Poxviridae* represent the largest family of viruses known to cause diseases in marine and terrestrial mammals [50]. Among cetaceans, the odontocetes seem to be more affected than the mysticetes [49]. Species of cetaceans reported to be affected by pox viruses, include Atlantic bottlenose dolphins [7, 50], bottlenose dolphins from Australia [49], Atlantic whitesided dolphins [7, 50], common dolphin (*Delphinus delphis*), dusky dolphins, white-beaked dolphins (*Lagenorhynchus albirostris*) [29, 50], striped dolphins (*Stenella coeruleoalba*) [29, 50], Hector's dolphins (*Cephalorhynchus hectori*) [7, 29, 50], long finned pilot whales (*Globocephala* 

Dolphin pox has been associated with a variety of lesions, referred to as 'targets', wateredsilk', 'ring', 'pinhole', 'circle' and 'tattoo'-like [7]. These lesions emerge as single or overlapping circular grey spots. Later, these ring lesions may develop into black punctiform stippled patterns. Histological studies revealed a thickened stratum corneum with ballooning degeneration, and eosinophilic inclusions containing virus particles, inside the cytoplasm of stratum intermedium cells. Studies on this disease pointed to one consistent feature; its relationship with compromised environmental conditions and consequent

Herpes virus had been reported as the causative agent of focal dermatitis in captive, as well as free-swimming beluga whales [51, 52]. Lesions caused by this virus appeared as multiple grey, raised, pale grey regions on the skin, which eventually ulcerated and healed very slowly. At the time of infection, these whales appeared to be in poor health and under stress. Histological analyses showed epithelial cells that underwent intercellular oedema, necrosis and the development of microvescicles. Prominent eosinophilic, intra-nuclear, inclusion

In cetaceans, papillomas have been reported on the skin, as well as the tongue, penis,

**5. Microbes causing skin lesions in cetaceans** 

*melaena*) [29, 50], as well as a few spp. of porpoises [50].

general health of affected individuals [7, 51].

bodies were evident in infected epithelial cells [51].

*5.1.3. Papillomavirus in cetaceans* 

pharynx and first gastric compartment [51].

**5.1. Virus infections of cetacean skin** 

next section.

*5.1.1. Dolphin pox* 

*5.1.2. Herpes virus* 

A southern right whale neonate that beached along the Southern coast of South Africa and suffering from extensive skin lesions were found to be infected with a number of cutaneous fungi including *Chaetomium globosum, Chaetomium murorum* and *Penicillium coprophilum* [44]. During the same period, another southern right whale neonate was found beached and suffering from a yeast infection caused by *Candida zeylanoides* [45]. In both cases the authors speculated about anthropogenic factors contributing to the condition of the animals.

Maldini and co-workers [46] reported on bottlenose dolphins living in Monterey Bay, California. Their research, conducted between 2006 and 2008, showed that approximately 90% of these cetaceans were characterized by skin lesions. They identified five skin conditions, with pox-like lesions being the most frequently found. The authors suspected that contaminants such as persistent organic pollutants (POPs) and heavy metals were contributing factors that weakened the immune systems of the dolphins, thereby rendering them more susceptible to viral infections.

A recent study on North Pacific humpback whales (*Megaptera novaeangliae*) examined bacterial species associated with the skin of these mammals [47]. It was found that healthy individuals were characterized by similar microbial communities, as opposed to healthcompromised individuals that harboured different populations. Also, the microbial populations on the skin of these animals were found to be different to that of the seawater, which led to the conclusion that the skin-associated bacteria were adapted to live on the epithelium and its constituents. The study also reported that the bacterial phylum found most on healthy individuals is Bacteroidetes*,* in contrast to the health-compromised individuals which harboured Gammaproteobacteria as the dominant group.

Cetaceans are also exposed to UV radiation and often exhibit lesions similar to skin cancer in humans [48]. Interestingly, cetacean species with darker pigmentation have less UVR induced skin damage. Also, latitude affects the incidence of this phenomenon, since UVR dosage at lower latitudes, are 5 times higher than at mid-latitudes.

A recent study by Fury and Reif [49] reported poxvirus lesions in two estuarine populations of bottlenose dolphins from Australia. This was the first report of poxvirus-like lesions in Australian cetaceans. Their results suggested that these infections were accompanied by climatic events, such as flooding in this case, which lead to lower water salinity and higher occurrence of dolphin pox. They concluded that diseases such as dolphin pox, might act as indicators of environmental stress.

It seems evident from the above mentioned studies that the occurrence and high prevalence of skin lesions in many cetacean populations are linked to environmental factors, including water salinity and temperature, as well as pollution and eutrophication. These skin lesions may be caused by a wide diversity of microbes that will be discussed in the next section.
